A cylindrical lock is typically one in which two holes are drilled into the door. A larger hole is bored into the door face and a smaller crossbore hole is bored into the door edge. Typically, the face hole is sized from 1.5 inches to 2.125 inches and is centered at 2⅜ inches or 2¾ inches from the leading edge of the door; this distance is referred to as the backset. Other, less popular, backsets are at 3¾ and 5 inch. Residential doors are normally prepared for 2⅜″ backset and commercial doors at 3¾″ backset. The cylindrical lock was invented by Walter Schlage in 1909. The bored cylindrical lock arose from a need for a more cost-effective method of locking doors. The previous norm, the mortise lock, which derived this name from the mortise you, must create in a door in order to install the lockset. A mortise is a deep cavity, usually rectangular, which is created in the edge of a door. The successful creation of the cavity can often only be achieved with specialized tools and skill; once created you can then install the lockset which is filled with levers, cams, and springs. Because of the complexity of the mortise device, and its higher manufacturing cost as well as it's more labor intensive installation made the bored cylindrical lock an ideal substitute, both in price and functionality. The great majority of locks now in use on residences is a variation of the cylindrical lock and is known as tubular chassis locks.
Both the mortise type locks and the cylindrical type locks have a common feature, both utilize a latching mechanism to keep the door closed. A latch is a type of mechanical hardware, specifically a fastener, which is used to join two (or more) objects or surfaces together while allowing for the regular or eventual separation of the objects or surfaces. Some common types of latches include: Spring Slam, Compression Draw (Over & Under-Center), and Rotary Cam. Latches range in complexity from flexible one piece flat springs of metal or plastic, such as are used to keep blow molded plastic power tool cases closed, to multi-point cammed latches used to keep large doors closed. There are many ways to obtain latches for various applications. A hardware store or distribution center is a convenient and cost effective way to find standard hardware. A latch typically engages another piece of hardware on the other mounting surface. Depending upon the type & design of the latch, this engaged bit of hardware may be known as a keeper or a strike. Latches are typically implemented with doors, more specifically door knobs and/or door locks. Generally, a door latch will be implemented to keep a door closed.
A doorknob is a popular type of handle used for opening and closing a door. In its simplest form, a doorknob provides only a place to grab so that the door may be pulled toward oneself. On most modem doors, however, doorknobs can be turned to operate a latching mechanism, which normally holds the door closed. A doorknob may also have a lock built in, though in some cases it is beneficial for the lock to be separate. Doorknobs can be difficult for the young and elderly to operate. If a person lacks a firm grip a doorknob must sometimes be operated using two hands. For this reason doors in most commercial and industrial buildings and in many households now use an operating lever, rather than a doorknob, as the lever does not require a firm grip. Levers are also beneficial on doors with narrow stile widths where the reduced backset leaves insufficient space to comfortably turn a doorknob. Most household doorknobs use a simple mechanism with a screw-style axle (also called a spindle) with two flat ends, to be threaded through the door latch, and two knob sides. The location of the doorknob on the door may vary between a few centimeters away from the door frame to the exact center of the door, depending on local culture or owner preference. The distance from the edge of the door to the center of the doorknob is called a backset. Knobs are attached on both sides by screwing them directly onto the axle, and then securing one or more retaining screws on the side of the knob's axle.
There are a number of problems that may arise with a door latch, whether during installation, or do to normal wear and tear. For example doorknobs sometimes lose traction, which can generally be repaired by replacing the screw, which prevents them from slipping on the axle. Sometimes a door won't latch closed unless you slam it, the strike plate mounted on the door jamb is probably out of alignment, this is usually caused by normal wear and tear of the strike plate of the door. One may correct this misalignment by slackening the strike plate screws and moving the plate adjustment in any direction. Another more cumbersome alternative would be to remove the strike plate, clamp it in a vise or other holding apparatus, and file the interfering edge of the plate.
In addition to normal wear and tear, doors, like windows, require precise measurements when being installed. A miscalculation of even a ⅛ of an inch could sometimes cause the door latch not to close. The present invention gives the user the ability to adjust a door latch, whether the malfunction is caused by normal wear and tear, or improper installation, via a bored cavity located on the face of the head portion of the door latch.